The present invention relates to an agricultural working machine with a device for adjusting the ground speed.
With agricultural working machines such as forage harvesters, there is a need to adjust the air pressure in the tires depending on the ground being driven over, in particular to reduce the stress on the ground. Lowering the tire pressure increases the ground contact area, which results in less damage being done to the ground being driven over. The tire pressure is increased for street driving, however, since a higher pressure is required at high speeds to prevent tire damage.
Publication DE 198 04 249 describes a device and a method for adjusting the tire pressure, with which the air pressure in the tire is adjusted—during travel—to the particular circumstances. The tire pressure is regulated as a function of specific state variables, such as axle load, speed, and tension force. Basically, the tire pressure should be adapted to the particular circumstances as quickly as possible, with as few driving interruptions as possible, and via remote control from the driver's cab.
The disadvantage of this embodiment is that it is not possible to adjust the tire pressure to changing circumstances immediately. With a forage harvester, for example, the tire pressure is reduced to approximately 0.8 bar while a field is being worked. If, on the other hand, the forage harvester is operated briefly in the street-driving mode when moving to a different field, a tire pressure control system, for instance, is unable—due to the tire volume—to briefly increase the tire pressure to approximately 2.5, which is typically required for street operation, or the driver simply drives to the other field without raising the tire pressure at all. When a forage harvester is driven at permissible ground speeds of up to 40 km/h with low tire pressure, however, the tire may detach from the wheel rim, particularly when driving around a curve, thereby endangering the agricultural working machine and the driver.